Keratoconjunctivitis sicca (KCS), or "dry eye", is an acquired condition of the elderly, principally affecting women, characterized by a spectrum of symptoms and signs including foreign body sensation, debilitating photophobia, and in severe cases visual loss from ocular surface breakdown. It has been estimated that this condition may afflict more than 15% of those aged 55 and over, and in the United States, over $100 million are spent annually on topical ocular lubricants alone. Despite this presumed prevalence of disease and associated health care costs, there have been no population-based estimates of the prevalence of KCS in the United States nor controlled studies directed at elucidating potential risk factors for this condition. We propose to examine a representative sample of 2,300 community dwelling persons age 65 and over. KCS will be assessed by means of a questionnaire, objective tests of tear function (Schirmer's testing, Rose Bengal scoring, tear film osmolarity, conjunctival impression cytology), and evaluation for evidence of primary or secondary Sjogren's syndrome. On the basis of these and related tests, we will estimate age-specific prevalence of KCS by categories of severity and associated disease. Previous laboratory or uncontrolled clinical studies have suggested possible risk factors for KCS including immune status, sex hormone status/reproductive history, systemic "drying" medications, smoking, and measures of oxidative stress. We will test these and other secondary hypotheses with a combination of questionnaires and serologic assays using nested case control studies.